Phenolic contribution of South African herbal teas to a healthy diet.

South African herbal teas, rooibos and honeybush, are increasingly enjoyed as healthy alternatives to Camellia sinensis teas. They contribute to the diet with bioactive phytochemicals not commonly found in foods. Major compounds of rooibos are the unique dihydrochalcone, aspalathin, and its flavone isomers, orientin and isoorientin. Honeybush contributes the xanthones, mangiferin and isomangiferin and the flavanones, eriocitrin, narirutin and hesperidin. All these compounds are either C-glucosides or O-rhamnoglucosides, which are poorly absorbed. Phase II metabolism and degradation by intestinal bacteria are important factors in their absorption. Modulation of drug metabolising enzymes is indicated which not only could affect the therapeutic window of drugs, but also the bioavailability of other dietary flavonoids.